1. Field of the Invention
The present invention relates generally to BLDC (brush-less direct current) motors, more specifically, the present invention relates to a speed-control circuit for BLDC motors.
2. Description of the Related Art
BLDC (brush-less direct current) motors are nowadays gaining popularity in automotive, consumer, and industrial applications. They have many advantages over traditional brushed DC motors, such as higher efficiency, linear speed and torque characteristics, low acoustic noise generation, wider speed range, less maintenance, and longer operating life.
Applications, such as ventilation system using BLDC motors as main ventilating component, suffer from magnetic aging problem. A long-term operation of the BLDC motor could cause its operation temperature to raise and reduce the magnetic force of its magnets. The operating speed of the BLDC motor might turn slower than its regular speed and therefore could dramatically affect the efficiency of the ventilation system.
Therefore, a control circuit capable of keeping the speed of the BLDC motor constant with simple design and low cost is desired by the industries.